The Venezuelan experience in the control of Schistosomiasis mansoni

Abstract

Schistosomiasis mansoni endemic zone of Venezuela is located in the valleys of the north central mountain region, with an extension of 15,000 km2 and inhabited by 5.1 million persons. The disease was discovered in 1906, but an organized Control Program was not established until 1943. Its basic activity has been the control of the snail vector, but prevention of man-water contact, prevention of snail infection, treatment of infected people and sanitary instruction, have also been carried out. Prevalence has diminished from 14.7% (1943-60) to 0.9% (1981-84). At present few active foci still persist, but a low transmission rate and low morbidity makes it difficult to know the exact number of infected people, which has been estimulated to be about 50,000

The Last Fifteen Years of Schistosomiasis in Venezuela: Features and Evolution

“…In fact, high focal transmission was found in some localities such as the Caracas valley with 29.1%, Aragua 24.8%, Miranda 10.3% and Carabobo states 9.9% (Incani 1987).…”

“…Reviews on the epidemiology of schistosomiasis in Venezuela have been reported by Luttermoser (1946), Jove and Marsewski (1955), Gabaldón (1964), Incani (1987), Balzán (1988), Noya et al (1991) and Rey (1992) among others.…”

“…The first control measures were initiated in 1922 in spite of the fact that the snail distribution was not known in the country. But only in 1943 the Schistosomiasis Control Program (SCP) initiated its activities as a formal structure in the Minister of Health (Incani 1987 later, in 1984, a group of investigators and people related to the Control Program, agreed to create the Schistosomiasis Research Group (SRG).…”

The efficacy of human schistosomicide treatment may depend on the rate of transmission

“…As a consequence, near 80% of infected individuals harbour low worm loads (<100 eggs/g of faeces), the majority being asymptomatic. Under these conditions, the coprologic detection of eggs (Kato-Katz) becomes inefficient (Incani 1987;Alarcón de Noya et al 2002). Serological tests like enzyme-linked immunosorbent assay (ELISA) with crude extract of adult worms or eggs have good sensitivity, but there is cross-reaction with sera of patients infected with other intestinal nematodes, a limitation that was improved by oxidation of carbohydrates responsible for the crossreactivity (Alarcón de Noya et al 2000).…”